HunterLab sphere instruments like the UltraScan PRO and UltraScan VIS do not fully comply with this method but meet many of the requirements of the USP 671 Light Transmission Test.

“Use a spectrophotometer of suitable sensitivity and accuracy, adapted for measuring the amount of light transmitted by either transparent or translucent glass or plastic materials used for pharmaceutical containers. In addition, the spectrophotometer is capable of measuring and recording light transmitted in diffused as well as parallel rays.”

To measure diffused and parallel rays, a sphere-based spectrophotometer is needed. The USVIS has a 150 mm (6 in) diameter sphere and meets this requirement when you measure in TTRAN transmission mode against the sphere.

The other requirement is the ability to measure and report transmission data over a short UV-VIS wavelength range of 290 nm to 450 nm in 20-nm intervals with maximum transmission dependent on vial size and intended use (see USP 671 Table 2). This requirement is partially met by the UltraScan VIS.

The USVIS has a wavelength range from 360 nm to 780 nm, reporting in 10-nm intervals. It does not meet the full USP 671 requirement. Many of our commercial customers use our instruments in QA labs with the assumption that if the % transmission relative to Air is <10% from 360 nm to 370 nm, then that level of transmission continues further into the UV.

They use a full UV-VIS spectrophotometer like a Perkin Elmer or Cary in the research lab to verify UV/VIS 290 nm to 450 nm range results for final reporting, but use our faster and more versatile USVIS in the QA lab for fast checks from lot-to-lot.

Here is how to setup the USVIS with EasyMatch QC software to take this measurement.

Install the HunterLab Transmission Clamp Accessory (C02-1005-444) at the TTRAN port, which is on the sphere side of the transmission compartment.

Standardize the instrument in Total Transmission (TTRAN) LAV UV Filter Nominal mode using Air as top-of-scale.

The first step in standardization is to block light getting to the detector using the black card as a physical reference for 0% transmission.

The second step is to place the white tile at the reflectance port to complete the sphere and measure Air at the TTRAN port as a physical reference for 100% transmission. Leave the white tile at the reflectance port for all subsequent sample measurements.

As a PQ Performance Qualification step after standardization, read Air back as a standard or sample. The 10-nm spectral data from 360-nm to 450-nm should be 100 indicative of Air as a clear and colorless medium.

Place the bottle cut-out in the transmission clamp at the TTRAN port against the sphere and make a color measurement. In the spectral plot, there should be a rapid fall-off below 400 nm to a defined level at 370 nm (typically under 10% transmission), indicating that there is a UV absorber present in the bottle cut-out and in sufficient amount to be effective in protecting the bottle contents.